Gas pressure seems very low.

On our recent trip on using the oven the gas was really low on the hob and when 2 hobs were lit the flame on the 1st one lowed even more. When last used about 4 weeks ago eveything was working fine. We are using butane gas and the flame is a steady blue colour and there  is no sign of yellow, as we have never had to replace a bottle before I was wondering could this be a sign that the gas is getting low or  is it more likely to be  another reason.