Not a problem. Teflon tape is fish safe, too.
Check the O-rings (if any) that are associated with those connections. Might be time for new ones. You can try adding a little petroleum jelly to them, too.
As the O-rings age they tend to take on the shape of where they are seated. When you have cleaned the filter, they may not reseat just right, but may twist into a new position, causing a leak. Vegetable oil or petroleum jelly makes them slide into place better, and they are more likely to reseat where they are starting to deform, and this can be a better seal. The petroleum jelly also adds just a little bulk to them, and if the leak is really slow this may stop it long enough for you to order new O-rings.