Hi and welcome to the forum
Fish rubbing on objects in the tank can be caused by external parsites or poor water quality. However, it's usually caused by external protozoan infections like white spot or velvet. These can be treated with heat (30C/ 86F for 2 weeks) or chemicals, but heat is safer than chemicals.
The following link has information about white spot.
This is a common question that is often asked, what is ich and how is it recognisable and what causes it? The real term is ICHTHYOPHTHIRIASIS. OR commonly known as white spot. It is an extremely comon parasite that affects aquarium fish. It is highly infectious and potentially lethal and...
www.fishforums.net
If you can post some pictures of the fish we can check them for white spot.
In the mean time, do the following.
Wipe the inside of the glass down with a clean fish sponge.
Do a 75% water change and gravel clean the substrate every day for a week or until we work out what is wrong. The water changes and gravel cleaning will reduce the number of disease organisms in the water and provide a cleaner environment for the fish to recover in.
Make sure any new water is free of chlorine/ chloramine before it is added to the tank.
Clean the filter if it hasn't been done in the last 2 weeks. However, if the filter is less than 6 weeks old, do not clean it. Wash the filter materials/ media in a bucket of tank water and re-use them. Tip the bucket of dirty water on the garden/ lawn. Cleaning the filter means less gunk and cleaner water with fewer pathogens.
Increase surface turbulence/ aeration to maximise the dissolved oxygen in the water.