Most algae problems are caused bi an imbalance---too much phosphate to nitrate. Many overseas sites suggest adding nitrate. JBL balls are micronutrients not macros.
They are an indication of overfeeding which will cause all sorts of other problems but not a problem in themselves. As E.coli indicate faecal contamination these indicate overfeeding.
It gives them a boost but also will kill them if you use too much. I don't know if it is the alcohol or CO2 that is produced but it becomes boom then bust for me.
First one could be banana plant too. The leaves are a bit small for cordifolius. You are probably right with the Ludwigia, the lack of red threw me, although they are red emersed as well (or mine were).
Plants can vary a lot under different growing conditions. I suspect the first one may be Echinodorus cordifolius (used to be called radicans), and the second may be Hygrophila corymbosa stricta but it is unusually compact and this can be caused by having a lot of blue light.
An interesting wee trip around beaurocracy: Maf to ministry of fish to Doc and back to ministry of fish who finally rang back today. A permit is required (lots of hassles the man said) from Fishserve (fishserve.co.nz) who are contracted to the Ministry of fisheries to administer their permit system.
It seems like a permit and quota is required to sell them but you can take them for your own use.
If you are aiming for soft water in your discus tank there may not be enough calcium for snails to keep their shells in good condition. Apple snails will probably not eat algae while there are still plants in the tank---but that will not be for very long.