Why are my plug plants going yellow??

Hi everyone, i am novice gardener, with the help of so many people in the forum, i hv managed to design my garden and planted plants and shrubs. Now comes the difficult part of looking after them.. and i m totally at loss.. most of my young plants leavss are going yellow. Its the old leaves but i think thr is a trend here and cant seem to undertand why... is it normal or is it lack of nutrients? I give dute fertiliser every 2 weeks as rcommended...
I will really appreciate your suggestions on what can be done...
Here are some pics

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I think you should lay off the fertiliser a bit, they need to establish first, fertiliser is not needed until later in the season when they have used all from the soil.

 

Hi I agree with Pam hold off the plant food and let them settle in and I wouldn't feed
nasturtium as you will end up with all leaves and very little flower

I think your last picture it looks like it has caught a chill how long have you had them outside as I only put out my annuals about two weeks ago

Most look like old leaves , so I wouldn't worry , all I would do if it doesnt rain !!!

give them a water but dont drown them

 

thanks @Spruce and @pamsdish
The last one is a perennial I got as a plug from T&M and I planted it out at the beginning of May... I will stop feeding them... just making sure nothing else is wrong here...

 

If T&M had the plants indoors when they sent them to you, and you put them straight outside, they would have got a shock, and that could account for the yellow leaves - the last one looks a bit like that. (They need hardening off - outside during the day, in at night, shelter from wind / breeze, after a week put out earlier / leave out longer, and risk leaving out on mild nights. After a couple of weeks they will be acclimatised.

Saw an interesting thing on Beechgrove a week or two back. They are doing a spot, each week, for a newbie gardening couple in a brand new house on a housing estate. Week1: Created the garden, Week2: planted it up, Week3: came back and asked "Any questions?"

The owner says "This plant isn't doing very well" and it sure was not! It was very small, and had presumable "lost weight" rather than gained / grown.

The presenter scooped it out of the ground, with his hand, and said "Stick it in a pot and give it some TLC for a bit". I expect that instruction would include "on the kitchen windowsill"

If you think that plant in the last photo is a bit weedy (it looks it to me - too small to be ready for being outside yet - but photo angles etc. can be deceptive) then maybe its a candidate for the "TLC Treatment"?