General statements like this are just IMO incorrect and misleading. First off light grows plants as well, we can have too little at times. If the plants are growing slowly then sometimes a little extra light could lead to better organic uptake, better growth and a cleaner tank. This extra light might be in the form of a 1-2 hour burst that might have a more positive aspect on plant growth than a negative aspect on algae. It really depends on the setup,
Also the comment about the 2 x T5 being enough light for that depth was made before even knowing what kind of T5 the OP was using. As we know now this varies tremendously by model/manuf.
It seems to me that alternative to giving specific advice is to say, "sorry, but your tank is different from all others, so you are just going to have to figure it all out for yourself. There are just too many variables for any of us to be able to offer you any help. But, don't ask me to define all of those variables, because only God knows them."
Everyone's advice here has some probability of being wrong. That is just a given.