Interesting. I would not have thought they (BBA) and stunted growth could be related. Is your BBA on the plants with the stunted growth?
the old classic CO2 deficiency is progressively smaller tip growth. With other species, the tip will completely stunt. Some species just sit and get algae covered and the aquarist thinks well.....I just cannot grow that plant.
Algae are also good indicators of stronger CO2 issues or a lack of ferts perhaps.
BBA is a strong indicator of a CO2 issue.
Some greens are tough once they enter due to a minor lull in CO2, say the 1st 1-2 hours of the light cycle(I have no reason to doubt this, but have little evidence to say so also).
Tweaking the CO2 has cured each and every green algae issue I've had other than Green water.
And 100% of all BBA issues I've ever had or anyone's tank I've served or helped in person. After 20 years, I think the record there is pretty strong.
Several plants might grow well also, but a few might not. Plants will and do compete with each other for nutrients/CO2, but light/CO2 more than anything. If they can start photosynthesis before their competitors..........then they can start taking up the CO2 1st...........leaving little for the other plants/species etc.
So a Myriophyllum might do very well, while the Downoi does poorly.
When everything grows well, then you know the CO2/ferts are not an issue.
that's what you are looking for.
Do this adjustment VERY SLOW, watch and observe, get the PSI up to the 30-40 range for those types of diffusers. I use mostly NW pumps and need only 10psi etc.