Dark green is very old and likely to be undersized by modern standards. It may also have a poor connection point.
Your photo does not show what they are attached to. It's possible that one of them is connected to something on or near the incoming electricity supply.
look carefully at the meter backboard for a durable label and see what it says.
Most likely you have a Main Earthing Terminal, which is not clearly shown in your photo but appears to be an old screw; and the cables to your consumer units come here, and the cable from wherever your earth is supplied. The cable that goes into the floor might or might not be connected to a water pipe, a gas pipe, and/or an earth spike.
Having established that, you could get a better MET and some larger cables.
An earth block like this
is better than the screw you currently have. It has ample capacity for multiple cables, each of them gripped by two good screws, and any one can be added or removed without disturbing the others. It can accept a 16mm cable which is the largest you are likely to need, and several 10mm which are likely to be correct for the main bonds for your incoming metallic services such as water, gas and oil pipes. Your house is old so it may have lead waste or iron soil pipes entering the bathroom from outside.
When connecting or disconnecting earth or bonding wires, do not touch the metal core or the earth terminal, because it is possible that there may be a voltage between them. The point of bonding them all together is that once fixed, there can be no voltage between them so they are safe to touch.
These earth clamps
are used for bonding to metal pipes (but not, please, the armour on a mains cable) and have a very useful durable identification label. The ones I show are corrosion resistant.
