Major disconnection issues with Yellight LED color bulb

I have the grey version of the LED color bulb and have 15 of them. Recently for the past one month From time to each one of these bulbs disconnect. I can’t control them through the app even though the Lan connection is enabled and my phone is connected to the same SSID as the bulbs.
The only way out is to turn the bulb on and off and they establish the connection. Then after some time, they disconnect it. I tried resetting them and connecting them and it does resolve my issues. All my other smart devices are working fine but the bulbs don’t.
They are all on the latest firmware and I am on the Singapore server. My MI ID No is 1733078537.

I have lot of automation and scenes and this is literally driving me crazy.

I used to have disconnects like 2 years ago (like, at least every couple of weeks, or sometimes daily) and since I got new router, I have almost never had disconnects (like one ceiling light disconnects twice a year, but in that room the signal is pretty weak). So there is big chance that your infrastructure/router are to blame. It is best to have separate router/access point for smart devices, especially if you have a lot of devices. Some routers just can’t handle more than 20-30 devices (due to small RAM amount or speed etc).

Thanks but I had the bulbs for over 4 years now and this is the first time I am having these issues.
So it’s definitely not the router.