You can access the properties of subplots by assigning handles, e.g.
fh = figure;
sfh1 = subplot(1,4,1);
sfh2 = subplot(1,4,2);
If you want to change size you can use the set()-command or the .-operator. Since subplots are made you have to consider to rearrange all of them manually since there is no check whether there is some overlap.
sfh1.Position = sfh1.Position + [0 0 0.05 0];
If you change order of commands as
fh2 = figure;
sfh3 = subplot(1,4,1,'Parent',fh2);
sfh3.Position = sfh3.Position + [0 0 0.05 0];
sfh4 = subplot(1,4,2,'Parent',fh2);
the second subplot sfh4 overrides the first sfh3, thus not all of the subplots are displayed.
fh3 = figure;
ah1 = axes('Parent',fh3,'Units','normalized','Position',[0.1 0.1 0.15 0.8]);
ah2 = axes('Parent',fh3,'Units','normalized','Position',[0.3 0.1 0.15 0.8]);
imshow(remdPic1,'Parent',ah1)
You could define the positions as dependent values. Adjustment might then be easier.