Did you check your water perimeters?
you didn’t mention your ammonia level, ph nitrate, nitrite
I would check these, and perform a water change if necessary
I have 2 well Planted 10 gallon aquariums It is not unusual for everything to go right for a good while then without notice suddenly encounter an ammonia spike and or high nitrate. Especially if I’ve over fed due to babies in the tank and or if I’ve neglected the hob filter.