Seem to be losing a lot of lower leaves on stems.
That means you are using too much light and that your CO2 and flow or distribution techniques are inadequate.
Saying that you use pressurized CO2 means nothing as an estimated 95% of all problems incurred in pressurized CO2 tanks are actually due to poorly implemented CO2.
There is an entire set of procedures that have been developed to help optimize the efficacy of CO2.
"Demanding" plants are demanding because they demand better CO2 techniques, not because they demand more light.
This is a fact that many hobbyists completely gloss over to the detriment of the plants and animals in the tank.
There is no such thing as "best T5 bulb for plant growth". Any T5 bulb you use will be fine and none will work better than any other.
The problem with T5 and other bulbs is that hobbyists tend to use too much light and then when their plants melt into oblivion they are then quick to offer ridiculous excuses such as macro or micro poisoning.
Best should be considered as what is best for you to look at.
If you are using 4 bulbs and are killing you plants with kindness, then it would be a good idea to disable two of the bulbs until you can sort out the problems with CO2/flow/distribution. Losing lower leaves is one of the first signs of impending serious problems.
Cheers,