Can't grow roses well on an enclosed balcony? With the right method, they'll still burst with blooms

I've been growing roses on an enclosed balcony for a year and a half. In the first month, I lost a Keira, and I culled Meikouguan and... (I forgot the name) because they nodded, had branches that were too soft, or grew too tall. My other roses have been growing healthily in my home all along. The roses I'm growing now are: Neptune King Balcony, Canary, Mercury King Balcony, Pluto King Balcony, Lapis Lazuli, Apricot Terrace, Fan, and Monte Carlo.

How enclosed my balcony is: glass starts 30cm above the floor, it can't be opened from 1.2 m above the floor, and above 1.2 m it can be opened and closed freely. It faces east, so it only gets half a day of sunlight.

1. About spraying

Everyone says roses are medicine jars. When I first started growing them, I also sprayed every half month (insecticide and fungicide), and the longer I've grown them, the longer the spraying interval has become. Now, I make sure to observe the roses once a day and check their leaves. If there are no pests or fungal damage, I stop spraying. I'm a bit slow, and I grow a mix of flowers at home, so I have the good habit of taking notes, recording which flowers were watered, sprayed, and fertilized on which day. I just checked my records. The most recent time I sprayed the roses was in mid-May, and it's been more than 4 months since then. The roses are very healthy and I haven't sprayed again. I have photos as proof.

2. About watering

From the picture above you can also see my watering frequency. In fact, I mainly judge by weight and use the date as a secondary reference. In summer the frequency is a bit faster, at other times it's a bit slower, on scorching days I check the weight more often, on cloudy and rainy days the frequency is a bit slower, and so on.

One thing is very important: watering must soak through, watering must soak through, watering must soak through. I personally feel that the biggest credit for the roses being healthy and not getting sick goes to watering.

Canary needs no further explanation, an essential product for home and travel. Apart from the flowers not being fragrant, it has no other faults

3. About light

As mentioned earlier, my home has an east-facing balcony with only half a day of sunlight, and all the roses occupy the most advantageous spots on the balcony to ensure as much sunlight as possible.

Monte Carlo: this flower grows rather wildly, and it seems more suitable for planting in the ground.

4. About fertilizing

I only use two kinds of fertilizer, a special organic nutrient solution and potassium dihydrogen phosphate, once every 10-15 days, and I stop using them in summer.

5. About soil mixing

This should have been placed earlier, but I won't edit it, so I'll put it here. It's basically nutrient soil : garden soil at 6:4, with some base fertilizer added casually. The garden soil is the fairly black composted layer under the trees in the park. I sift it once with a sieve to sift out insect eggs and such.